Means for forming and securing turbine compressor blades

ABSTRACT

THE INVENTION IS A FORMING DIE FOR USE IN FABRICATING COMPRESSOR BLADES FROM SYNTHETIC FIBERS. SUCH FIBERS ARE SPACED A DETERMINED DISTANCE APART AND FORMED INTO A WEB WHICH IS HELD IN FIXED POSITION APPROXIMATING THE SHAPE OF THE FINISHED BLADE AND THEN IMPREGNATED WITH A BONDING AGENT TO PRODUCE AN INTEGRAL BLADE WITH REINFORCED BLADE PORTIONS AND ROOT PORTIONS. THE INVENTION INCLUDES MEANS FOR MOUNTING BLADES TO A ROTOR BY SECURING A SPLIT BUSHING WITH OPPOSITELY DISPOSED CONICAL BORES IN THE BORE OF THE BLADE ROOT, INSERTING AND SECURING THE BLADE ROOT IN A KEYHOLE SLOT IN THE ROTOR AND BY FORCING THE CONICAL WEDGES TOGETHER IN SAID BUSHING.   D R A W I N G

S. MOTTA March 13, 1973 MEANS FOR FORMING AND SECURING TURBINECOMPRESSOR BLADES Filed April 28, 1971 2 Sheets-Sheet l Him.

INVENTOR. SALVATORE MQTTA l'luv n. P

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March 13, 1973 s MOTTA 3,720,481

MEANS FOR FORMING AND SECURING TURBINE COMPRESSOR BLADES Filed April 28,1971 2 Sheets-Sheet Z I N VEN TOR. SALVATORE MOTTA ATToxEYs.

United States Patent 3,720,481 MEANS FOR FORMING AND SECURING TURBINECOMPRESSOR BLADES Salvatore Motta, Commack, N.Y., assignor to AvcoCorporation, Strattord, Conn. Filed Apr. 28, 1971, Ser. No. 138,241 Int.Cl. F0111 5/32 US. Cl. 416-220 3 Claims ABSTRACT OF THE DISCLOSURE Theinvention is a forming die for use in fabricating compressor blades fromsynthetic fibers. Such fibers are spaced a predetermined distance apartand formed into a web which is held in fixed position approximating theshape of the finished blade and then impregnated with a bonding agent toproduce an integral blade with reinforced blade portions and rootportions. The invention includes means for mounting blades to a rotor bysecuring a split bushing with oppositely disposed conical bores in thebore of the blade root, inserting and securing the blade root in akeyhole slot in the rotor and by forcing the conical wedges together insaid bushing.

BACKGROUND The design and fabrication of compressor blades particularlyfor gas turbine engines creates many problems in insuring that theblades are sufiiciently strong to withstand the enormous centrifugalforces created by rotating them at high speed, particularly in the rootportions thereof. While special metal alloys have been developed whichare generally satisfactory in this environment, there is a distinct needfor still tougher and more reliable blades and blade mounts. Whatevermaterial such blades are made of, there is a continuing need forpositive means by which such blades, which must be independentlyfabricated, can be rigidly effectively secured to a rotor and yet becapable of easy removal therefrom.

THE INVENTION AND ITS OBJECTS The invention seeks to resolve theproblems heretofore experienced in fabricating compressor blades, and ineffectively securing them to a rotor in easily removable fashion.

Objects of the invention include the provision of a forming die whichwill permit synthetic fiber filaments to be held in alignment in webform for impregnation with a bonding agent, with the filaments beingaligned in the direction of the highest stresses when these occur indifferent planes during turbine operation.

Another object is to provide an anchoring device for such blades whichwill bring out the full strength of the filaments and which will at thesame time be free from notches and sharp corners which deleteriouslyaffect the performance of the blades in use.

An additional object is to provide a mounting for such blades in a rotorby which the blades are very firmly secured against displacement bycentrifugal forces .and yet are easily removable for repair orreplacement.

These and other objects of the invention will more clearly appear whenreference is had to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an elevational view partlyin section of a forming die assembly by which a synthetic fiber web issupported for integration with a bonding agent into a unitary compressorblade.

FIG. 2 is a plan view of the device of FIG. 1.

3,720,481 Patented Mar. 13, 1973 "ice DETAILED DESCRIPTION Referring toFIGS. 1 and 2, a synthetic filamentary material such as boron, which hasbeen wound into a continuous web 10, with the filaments held apredetermined distance apart by coating with a bonding agent, is cut at11 and placed in a fixture 12. The fixture is provided with a mandrel 13journalled in bearing blocks 14 and a clamping device 15, which istightened by a bolt 16 and adjusted by spring pressed means 17. Themidpoint of the web is disposed around a split bushing 26 of specialconfiguration which, in turn, is slipped over the mandrel 13, and theends are clamped by means 15 and 16. The web is placed in suitabletension and the clamp 15 twisted on its axis 18 to effect the desiredpitch of the blade to be produced.

Die blocks 19 and 20, having inner surfaces 21, machined to produce thedesired fairing, are then brought together and secured by conventionalmeans so that the twisted web is held securely in place and its contourdefined by the die faces.

The assembly is then treated with a bonding agent as by immersing in acrucible of molten aluminum and permitting the aluminum to infiltrate inthe spaces between the blocks. It is then removed and cooled and theblade thus formed taken from the fixture 12, the mandrel 13 removed andthe blade properly trimmed.

The result is an integral blade with filament reinforcements aligned inthe direction of highest strength not only in the blade portion, but inthe root, since the re inforcing filaments extend circumferentiallytherearound and with the specially designed split bushing securedtherein.

Referring to FIGS. 3, 4 and 5, a blade 20 is illustrated as comprising ablade portion 21 and a root portion 22. The root portion has a circularbore 23 in its base of a dimension determined by the diameter of themandrel 13.

It is important to note that the split bushing 26 is split at 26a (FIG.'5), and has oppositely tapered axial openings 27 and28. The rootportion 22, with the split bushing firmly embedded therein, is nowinserted axially into a key hole slot 24 in the rotor 25 and assumes theposition shown in FIG. 5.

Conical wedges 29 and 30, having a central bore, are then inserted in anopposite axial direction in the bushing 26 so that the exterior surfacesof the wedges meet the internal surfaces of the bores 27 and 28. One ofthe wedges is threaded as at 31, while the other is smooth and is ofslightly larger diameter than the bolt 3-2 which extends therethroughand is screwed into the threads of wedge 30.

It will be observed that provision has now been made for a solidconnection of maximum strength between the rotor and the blade, not onlyby reason of the split bushing configuration, but also because thefilaments act as reinforcing ribs which lie circumferentially of theblade root and circumscribe the bushing. Bolt 32 is simply torqued toexpand the bushing. The expansion need be only .001" or .00 but is stilleffective to produce an exceedingly strong connection, which connectionis adapted to be adjusted during turbine shut-down or to be removed orreplaced where inspection and repairs become necessary.

Having thus described my invention, I claim:

1. A compressor blade assembly comprising a blade integrally formed of aweb of synthetic filaments disposed along the lines of maximum bladestress and infiltrated with a bonding agent, said blade having fairedportions and root portions, a rotor, a keyhole slot in said rotor, saidroot portion being disposed in said slot and having a cylindrical borelengthwise thereof, a cylindrical split bushing secured in said bore,said bushing having axially located, 1

oppositely disposed cone-shaped openings therein, Wedges disposed insaid cone-shaped openings, and means extending through one wedge andadjustably connected to the other to draw said wedges toward each otherto securely fix said root in said slot.

2. The assembly according to claim 1 in which the synthetic filamentsare composed of boron.

3. The assembly of claim 2 in which the bonding agent is aluminum.

References Cited UNITED STATES PATENTS 2,656,146 10/ 1953 Sollinger416-220 X 2,859,936 11/1958 Warnken 416-230 X 2,868,439 1/1959 Hampshireet a1. 416-230 X 2,995,777 8/1961 Warnken 1836 3,057,767 10/1962 Kaplan4l6230 UX 3,098,723 7/1963 Micks 416-241 X 3,600,103 8/1971 "Gray et a14l6--230 X 3,616,508 11/1971 Wallett 416230 X FOREIGN PATENTS 426,76311/1947 Italy 4162l9 5 EVERETTE A. POWELL, JR., Primary Examiner U.S.Cl. X.R. 4l6230, 207

